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Milky Way on the Dorset Coast


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There seem to be a few 'Just got back from ... and here's the Milky Way' pics and here's my addition.

I've just had a couple of nights on a campsite near Burton Bradstock. Two beautifully clear nights (why is that never the case when I want to set up in my garden!) and I couldn't resist a play with the holiday snap camera, a 700D with an 18-135mm lens. I shot this at 18mm, f5, 3200ISO, 30 x 20s lights with 20 darks. The subs were fine in the corners, but when I stack them all in nebulosity 3, I end up with streaky stars at the edges. Any thoughts why this happens and how I can avoid it?!

post-29321-0-38257400-1409611314_thumb.p

I'm thinking that this could probably benefit from a visit to HLVG, but I'm on the mac and it doesn't exist for the mac, darn. I'll give it a try next time the PC is on!

Thanks for looking and here's to always getting an astro fix wherever you may be!

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Thank you.

@Mookie - you lucky thing, some wonderful dark skies down there. I had a lovely couple of days, thank you, though wasn't brave enough to go in the sea!

@Paul - Ha ha, like that idea! No, didn't go to the Beach Hut... Sounds like I missed a treat there.

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Lovely picture Gav. I was down in Dorset recently and had fabulous views of the Milky Way down to the sea from near St Aldhelm's chapel. I will be going back!

EDIT Look carefully and you can pick out the Lagoon, Trifid, Omega and Eagle nebulae, plus M24 and M23. Nice :-)

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There seem to be a few 'Just got back from ... and here's the Milky Way' pics and here's my addition.

I've just had a couple of nights on a campsite near Burton Bradstock. Two beautifully clear nights (why is that never the case when I want to set up in my garden!) and I couldn't resist a play with the holiday snap camera, a 700D with an 18-135mm lens. I shot this at 18mm, f5, 3200ISO, 30 x 20s lights with 20 darks. The subs were fine in the corners, but when I stack them all in nebulosity 3, I end up with streaky stars at the edges. Any thoughts why this happens and how I can avoid it?!

The star smearing looks a bit like tangential astigmatism although it's well uneven.

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Interesting Mike and a great expression whether right or wrong! Though I think that it is a problem introduced in the stacking and not an inherent problem with the optics as each individual sub looks absolutely fine. It is the stacked image that displays the problem...

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Actually... I've thought about it a bit longer and from what I remember of the subs (currently on the ipad, subs are on the mac), there is some coma in each sub. There is also some star trailing with the 20s exposure (should have settled for shorter!) especially at the edges of the field. Stacking together the 30 subs has massively emphasised the coma and trailing. The question is how to eliminate these things!?

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Lovely picture Gav. I was down in Dorset recently and had fabulous views of the Milky Way down to the sea from near St Aldhelm's chapel. I will be going back!

EDIT Look carefully and you can pick out the Lagoon, Trifid, Omega and Eagle nebulae, plus M24 and M23. Nice :-)

Thank you! Yes, if you look really carefully and squint a bit to counteract the stretchiness, those objects are in there. It's a great area, both of sky and land, will certainly be returning too!

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Actually... I've thought about it a bit longer and from what I remember of the subs (currently on the ipad, subs are on the mac), there is some coma in each sub. There is also some star trailing with the 20s exposure (should have settled for shorter!) especially at the edges of the field. Stacking together the 30 subs has massively emphasised the coma and trailing. The question is how to eliminate these things!?

That could well be it.

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Thank you.

@Mookie - you lucky thing, some wonderful dark skies down there. I had a lovely couple of days, thank you, though wasn't brave enough to go in the sea!

@Paul - Ha ha, like that idea! No, didn't go to the Beach Hut... Sounds like I missed a treat there.

Yep, I am very lucky and really love living here, especially after living in London for so many years. Plenty of beautifully dark nights, perfect for star gazing. Although i've never taken as stunning a photo as you did of the night sky..... but then I don't have a decent camera set up, so that explains it lol

FYI, the Beach Hut is over priced and over rated, so you didn't really miss out.

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Nice shot, hope you had a good holiday.

On the "coma" I'm wondering if it's a stacking artifact, I don't get that much even with my kit lens wide open. I notice your landscape is sharp, did you blend in a single exposure afterwards? If not, could it be aligning on the landscape rather than the stars? I haven't used Nebulosity, but you might want to try a quick stack in DSS.

My only other thought is that could the focal length been changed a touch between subs?

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Thank you Knight - yes, a lovely couple of days.

I agree that this has to be a stacking issue as the subs really aren't too bad at all, perfectly acceptable. It's only the stacked image that has the problem. I will give DSS a go... Though I don't even have that on the PC yet, so a bit of learning will be required first!

Yes, I blended in the foreground to the stacked image, which had a blurred foreground.

Pretty certain the focal length didn't change.

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OK, so I tried a new version with DSS:

post-29321-0-25148000-1410204544_thumb.p

Definite improvement, but still not perfect, there's still some streaky stuff going on around the edges. I will blame my tools for a bit of that!

As an aside, I've never used DSS before and I have to say I'm impressed. It was pretty easy to pick up and use and has done a better job of this one than Nebulosity3. I'll have to give it a go with some other projects.

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